Neutron-scattering study of spin correlations in La_{1.94 - x} Sr_x Ce_0.06 CuO₄

We performed a neutron-scattering experiment to investigate the effect of distortion of CuO₂ planes on the low-energy spin correlation of La_{1.94 - x} Sr_x Ce_0.06 CuO₄ (LSCCO). Due to the carrier-compensation effect by co-doping of Sr and Ce, LSCCO has a smaller orthorhombic lattice distortion compared to La_{2 - x} Sr_x CuO₄ (LSCO) with comparable hole concentration p. A clear gap with the edge-energy of 6-7 meV was observed in the energy spectrum of local dynamical susceptibility χ^″ (ω) for both x = 0.18 (p ∼ 0.14) and x = 0.24 (p ∼ 0.20) samples as observed for optimally doped LSCO (x = 0.15 - 0.18). For the x = 0.14 (p ∼ 0.10) sample, in addition to the gap-like structure in χ^″ (ω) we observed a low-energy component within the gap which develops below 2 - 3 meV with decreasing the energy. The low-energy component possibly coincides with the static magnetic correlation observed in this sample. These results are discussed from a view point of relationship between the stability of low-energy spin fluctuations and the distortion of CuO₂ planes.